The present invention relates to a numerically controlled machine tool and machining methods thereof, whereby a long bar stock is cut into workpieces of a predetermined length, and the workpiece produced by cutting is carried to a spindle so as to machine.
One of the conventional machining methods on a bar stock is that one long bar stock is sawed with a sawing machine, whereby many workpieces of a predetermined length are produced from the bar stock, then those workpieces are loaded to a lathe by a worker. However, the work from production of workpieces (sawing of a bar stock) to machining on the workpiece in a lathe takes a long time to complete because stock control, warehousing control and goods control for a lot of workpieces are complicated.
Another conventional method of machining of a bar stock is that a bar stock is loaded from the back hand of a headstock passing through a hollow spindle with a bar feeder, the long bar stock is rotated as it is, and the portion of the bar stock, projecting into a machining area in front of the spindle, is machined, thereafter, the machined portion of the bar stock is cut off by turning. However, it is not possible that the spindle can be rotated at high speed in case of machining since a long bar stock tends to vibrate. Besides, in case of change of a kind of a bar stock, setting up, such as exchange of a filler tube in the spindle for preventing vibration, takes a long time.
A patent application No. Tokukaihei 3-111101 shows another conventional method of machining of a bar stock. That is, in this method a bar stock is supplied for the front face of a spindle without passing through the spindle and the bar stock is cut by turning so as to machine. However, in this example, it is necessary to pass a long bar stock into a hollow high rotational supporting apparatus in order to cut by turning, whereby this invention can not be flexibly applied to change of a kind (such as diameter) of a bar stock.